We continue to use the isolated rat liver perfused with a suspension of bovine red cells in a 3 percent solution of bovine serum albumin in Krebs- Ringer bicarbonate buffer as a basic model system for evaluating hormonal and other factors which regulate net biosynthesis of specific plasma proteins. Studies of hormones are to be extended to include secretin (pancreozymin), prostaglandins E2 and F2 alpha and serotonin. We are exploring one possible mechanism of induction of increased synthesis of acute phase proteins by glucocorticoid which invokes increased amounts of specific messenger RNA's. Techniques of affinity chromatography and immunochemistry utilizing antibody globulins specific for each acute phase plasma protein are to be used in direct attempts to isolate and quantitate corresponding mRNAs. Effects of hormones on synthesis of plasma proteins are to be correlated with net changes in free amino acids, glucose and urea to permit an overall estimate of nitrogen balance for the perfusion system.